In a wide variety of medical and laboratory applications, reflectance-based systems, often referred to as “reflectometers” are used to perform tests. In a typical form, a reflectometer includes one or more light sources configured to generate one or more light signals at given wavelengths. An object under test receives the signal and reflects a portion thereof. One or more detectors or sensors are oriented to receive the reflected signals. A processor analyzes the characteristics of the received reflected signals and produces a test result.
Such reflectometers are sometimes used for performing tests on a reagent test strip. In such a case, the test pads on the test strip may be incrementally tested to determine the presence of analytes in a liquid test sample absorbed into the test pads. Such systems may be used for performing urinalysis tests, as one example. That is, the level or presence of an analyte in a liquid test sample can be determined by causing a given test pad to absorb some of the liquid test sample, (e.g., a sample of urine) and then by reading associated reflectance values for the test pad with a reflectometer. Based on the reflectance characteristics of the signal reflected by the test pad, the reflectometer determines the presence or level of the analyte in a given test pad. As an example, a test pad changes color to indicate the level or presence of the analyte in response to absorption of urine from a urine sample. The characteristics of a reflected signal are a function of the make-up and color of the test pad and the wavelength of the light source. Consequently, a change in color of a test pad causes a corresponding change in the characteristics of the reflected signal.
Test strips are typically produced according to industry accepted formats. In the case of urinalysis reflectometers, test strips can come in formats having different lengths, such as, for example, 3.25 inch lengths or 4.25 inch lengths. Within each format, a test strip is defined according to its configuration, i.e., the number, types and order of test pads included on the test strip. Generally, each test strip configuration is uniquely identified. Implicit in a test strip identification and/or confirmation, therefore, is the test strip format and the test pad configuration. As will be appreciated by those skilled in the art, such test pads may include, for example, pH, ketone, nitrite, and glucose test pads. In order for the reflectometer to produce valid results, the test strip must be identified by format and configuration, so that the reflectometer has a proper context to evaluate the received reflected signals, or reflectance values derived therefrom. That is, a reflectometer needs to know that a received reflected signal is produced by, for example, a glucose test pad or a ketone test pad.
Reagent cassettes can also be tested using a reflectometer, in a manner very similar to that used for the test strip. Such reagent cassettes include a test region that provides visual indications of test results, similar to the test pads of the test strips. The test region can produce a series of lines that embody the test results.
There is a variety of known ways that the test strip is identified to or by the reflectometer. In some reflectometers, an operator enters data into the reflectometer that indicates the identification of the test strip from a look up table, or chooses the identification from a set of predefined options. The same can be done for reagent cassettes. The reflectometer is then ready to process the test strip or cassette. Other reflectometers include more automated mechanisms for determining the identification of the test strip. As described below, these various prior art automated reflectometers have certain drawbacks.
U.S. Pat. No. 4,592,893, as an example, discloses a test strip having a test field and a separate bar code for storing batch-specific information necessary for the quantitative evaluation of the reactions carried out on the test field. A narrow bar in the bar code is interpreted as logical 0 and a wide bar is interpreted as a logical 1. The binary code embodied in the bar code corresponds to the batch-specific information imputed to the test strip.
U.S. Pat. No. 5,126,952, as another example, discloses a method of providing data in a bar code form on a test strip useful for the determination of a lot of test elements for use in a chemical analyzer. A calibration curve corresponds to a given formula and its solution for a given lot of test elements is represented in a single bar code strip of only a few digits that accurately provide a calibration code for that lot of test elements.
U.S. Pat. No. 5,945,341, owned by Bayer Corporation of Elkhart, Ind., discloses an automated approach to reading a test strip wherein at least one test field and at least two marker fields are included on the test strip. The marker fields reflect light at specific ranges of wavelengths which differ from each other in a coded sequence of spectral regions that correlate to information about the test strip. A test strip reading device reads spectral reflectance values from the test and marker fields individually to identify the test strip, i.e., by moving the test strip with respect to a reading means.
The automated approaches for determining the identification of or information about a test strip provided to date require non-standard modifications to include bar codes, marker fields, test fields or some combination thereof. In some cases, there is no ability to add a bar code to an existing test strip. Therefore, certain non-standard test strips may only lend themselves to automated identification in certain non-standard reflectometers. And, certain standard test strips may not be identifiable by such automated systems. Even in properly equipped devices, the process of reading such fields can require multiple readings of the various areas of the strip to determine its identification. For the most part, operators of such reflectometers are required to have at least a minimum skill level necessary to identify test strips and conduct tests, in some cases certain certifications may also be desired. Identification of the test strips is required to achieve accurate and reliable test results. Systems tailored for specialized non-standard approaches tend to increase complexity.
It would be advantageous to eliminate some of the complexity inherent in such prior art approaches. In doing so, the required skill level, and possibly certifications, of the operator may be reduced. It would also be advantageous to provide a system and method that are not inherently limited to a subset of non-standard identification approaches, such as bar codes, test fields, marker fields or various differing implementations of the foregoing.